如何使用npm卸载全局软件包？

我以这种方式安装了webpack：

npm install -g webpack

现在要卸载它：

npm uninstall -g webpack

再次检查，它没有被卸载：

webpack -v
3.1.0

为什么？

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而且，我用这种方式找不到webpack：

npm list -g | grep webpack

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这也不起作用：

npm uninstall -g webpack --save

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在包含以下内容的目录下运行此文件后package.json：

npm uninstall webpack
npm WARN babel-loader@6.4.1 requires a peer of webpack@1 || 2 || ^2.1.0-beta || ^2.2.0-rc but none was installed.
npm WARN uglifyjs-webpack-plugin@0.3.1 requires a peer of uglify-js@^2.8.0 but none was installed.
npm WARN uglifyjs-webpack-plugin@0.3.1 requires a peer of webpack@^1.9 || ^2 || ^2.1.0-beta || ^2.2.0-rc but none was installed.